Chuck and Ryan's Build Tips

[ceslaw]

Rudder Cable Pattern

Yes, I admit it. This is probably over the top.

I have a bit of an obsession with making patterns.

The build manual has precise dimensions locating the point where the rudder cables emerge through the fabric. But I will sleep easier knowing that I have a pattern pin pointing the location, which was made before the fabric was applied.

A slot was cut in a section of grid board / poster board and the cable passed through and connected to the rudder. Then the poster board was clipped to the frame. An outline of the frame was traced on the backside and the poster board cut along the line. I now have an exact pattern of where the cable will emerge eliminating any doubt about the cable location when that hot soldering iron is used to melt the slot in the fabric.

Oh, and by the way, the dimensions in the manual pretty well matched the pattern dimensions.

[c130jake]

Good stuff, just wish you started before me. :-)

Jake


Sent from my iPad using Tapatalk

[ceslaw]

Body Filler

With the extended baggage using body filler to smooth the transitions is necessary. But while we had the body filler handy, it was applied in some other places as well.

DSC_0806.jpg

On the left side it was used to smooth the seam between the carbon fiber window sill and the fabric support.

DSC_0807.jpg

It was used at the junction between the stringers and their supporting tubes near the tail, including the vertical stabilizer / stringer junction.

The leading edge of the left wing tip did not match up with the leading edge skin as well as we liked. Thin pieces of aluminum were placed under the skin to keep it flat when riveted in place. This left a 1/16 inch edge where the two met. This variation was evened out with a bit of filler.

DSC_0107.jpg

I am partial to Rage light weight body filler, having used it on our GT40. It is easy to work with and light weight and is a polyester based product like what Cubcrafters uses.

DSC_0808.jpg

Minutes after applying a liberal (I hate that word) coat with a plastic spatula (a hotel card key also works well in smaller places), what looks like a cheese grater is used to roughly shape the surface close to the desired final surface, then before it is fully set up some 40 grit and 80 grit paper. By the time it is dry it is close to its final shape. It is finished with 180 grit followed by 320 or 400 grit. When done it is a nice smooth surface.

Per Mitch, no primer or paint should be applied because it will interfere with the Poly Fiber adhesive.

[ceslaw]

Map Pockets

After a lot of searching and ordering some that did not measure up to their advertising, we found storage pockets that look like they are up the Carbon Cub standards. They are made in Italy. One is curved, making it a perfect fit for the rear of the seat. The other is flat, 14” x 7”.

DSC_0149.jpg

Google “Britta Products Map Pockets” and a number of suppliers will pop up.

The map pockets were mounted using 8/32 stainless hex head screws and hardware. Note that on the side panel the top side screws need to be placed ¼ to ½ inch wider than the distance between the holes to assure that the sides are parallel. I suspect that the tension of the elastic net causes the sides to flex inward. .

By laying out the location carefully you can avoid hitting any vital organs behind the interior panel skin

DSC_0130.jpg

DSC_0146.jpg

The curved map pocket is an ideal fit on the back of the seat. But we really did not want to take the seat apart to tighten a nut on the back side of the seat frame. So instead nutserts were used. After drilling the holes a bit of epoxy was used before they were tightened in place. Unless someone gets really aggressive this should work just fine.

DSC_0137.jpg

DSC_0142.jpg

DSC_0156.jpg

[ceslaw]

Garmin G3X preparation

We decided to go with the Garmin G3X after checking it out at Oshkosh this summer. It has an abundance of features which are unnecessary for typical VFR flight but it is intuitive and packs so much information into such a small space. Before covering the plane there are three items that need to be installed.

1. Trim indicator. This provides a display on the G3X showing the relative position of the stabilizer trim. Once the indicator was installed the wires that run along the left stringer could finally be tied down. We used wire ties about every eight inches, wrapping the wire with friction tape at each mounting point.

A couple of notches were filed on the bottom bracket so a screw driver could be used to fasten the sensor to the vertical bracket.

DSC_0070.jpg

DSC_0074.jpg


2. Pitot tube. The AOA requires a two tube rather than single tube pitot. The bracket was mounted roughly centered between the inboard rib and the inboard edge of the landing light opening (which pretty much nailed the specs in the new drawings, which we did not have at the time). The bottom of the bracket must be even with the bottom of the ribs, not the spar. Masking tape between the ribs provided a good reference point for the bottom of the bracket.

DSC_0059.jpg

The pitot tubes were routed and then brought through the butt rib at the opening by the drag wire after a grommet was placed in the opening. Protective anti chafe wrap was used on the tubes. Silicone was applied in a couple of locations to make sure the tubes stayed put.

DSC_0104.jpg

DSC_0099.jpg


3. Magnetometer. First a couple of holes need to be drilled in the spar to mount the bracket. Very precise dimensions are specified to assure it will be level to compensate for the dihedral. (Future kits will have these holes pre drilled at the factory). The truth is the holes are slightly over sized so the bracket can be leveled even if the holes are a few thousandths off. Second the bracket needs to be assembled. We placed the three rivets on the leading edge and the top ring, but not on the sides. Once it is installed after the plane is covered the longitudinal axis can be checked to confirm it will be level in flight and then the four side rivets can be placed. Finally the cable needs to be run and secured with silicone.

DSC_0096.jpg

DSC_0098.jpg

Although the holes in the spar need to be drilled before covering, the magnetometer and the bracket are not permanently installed until the plane is covered. The risk of damaging it while covering is too great. The bracket and magnetometer need to be installed in the covered plane together, so there is no point in leaving the bracket in place while the plane is being covered.

The wings and fuselage are now ready to be covered.

[ceslaw]

Wing and fuselage rotator

The wing and fuselage rotators for the Carbon Cub recently became available, so I ordered one from Bogert Aviation Inc. It seemed a bit pricey, but it is specific to the CC and works with both the fuselage and the wings. I wish it would have been available sooner. It would have made assembling the fuselage easier. Being able to rotate it 360^ and raise the lower the ends is quite useful.

It is nicely designed and well fabricated. It ships in two small but heavy boxes. You must supply the 17’ long 1 ¾ tube.

I will likely put mine up for sale once the Cub is completed next summer, so there is no need for anyone reading this to rush out and buy one.

DSC_0195.jpg

DSC_0192.jpg

[ceslaw]

Poly Tak first impressions

Yes, I did go to the weekend Poly Fiber course at KOSH last January during that sub zero cold spell, but with a couple of dozen students it was mostly observation and not much hands on.

It was with some trepidation that I did my first fabric application, despite having watched the Poly Fiber video, Zack Carbon Cub video, and the Mitch Travis award winning video several times each. For those that have done it, these observations are probably old school, but for novices, here are few points.

1. Get an infrared temp gun. I tried a cooking thermometer (per the Poly Fiber manual), bi metal contact thermometer and finally the infrared thermometer. The first two were a pain because they take time to respond and because the iron temperature fluctuates. But shoot it with the infrared and you have a prompt reading. Instant gratification. It is surprising how much the iron will fluctuate, but with the infrared one can quickly adjust.

DSC_0210.jpg

2. MEK stinks. I started with an experimental section about a foot squared on a wooden frame. It took about an hour to cover it, after which I smoothed the edges with MEK. It looked great. There was good ventilation with an exhaust fan.

Then I left the shop and noticed a sensation of shortness of breath. Nothing severe, but it was a distinct sensation. It was the MEK. Nasty stuff. Now when I pop the cap on the bottle I have a respirator on and don’t take it off until the air has had time to clear.

3. It is worth spending a lot of time with the hobby iron smoothing seams and glued stringers. The comment “if you can feel it you will be able to see it when covered” is valid.

4. Wiping an exposed seam with MEK will smooth it down, but too much and it will loosen the connection.

5. I try to avoid putting glue on top of the fabric (contrary to the Carbon Cub videos) unless it is really necessary. Glue on top gums up the iron when trying to smooth the fabric and I’m not sure it adds to the strength of the connection. Of course there are exceptions, like the area around the landing gear.

6. Get a bunch of brushes and just pitch them after a fabric covering session

7. Wick’s sells nice specimen cups with covers which make nice Poly Tak containers. A hole in the lid will keep it fresh with the brush inside. Like the brushes, just toss it after a day’s use.

DSC_0211.jpg

8. When gluing fabric on fabric a length of masking tape along the glue line helps keep the glue where you want it.

DSC_0207.jpg

9. Wipe up drips of glue with MEK preferably before it dries.

10. Poly Brush likes to run. Try to rotate so that the surface is horizontal where the Poly Brush is applied.

11. With the fabric applied there were lots of wrinkles. I had some doubts about whether they would all iron out, especially at the curve at the base of the rudder. With the first 250^ iron they all pretty much disappeared. With the 350^ iron the fabric was a tight as a drum. Cool.

DSC_0216.jpg

DSC_0230.jpg

[c130jake]

Now it's starting to look like an airplane!


Sent from my iPad using Tapatalk

[ceslaw]

Now it's starting to look like an airplane!


Sent from my iPad using Tapatalk

hope to start covering wings in the next week or so.

[ceslaw]

Extended Baggage Fabric
The fabric around the extended baggage door presents some challenges. Here is what I learned:

1.Apply light weight body filler around the opening to assure an absolutely smooth surface. Any imperfections will show through. I final sanded it with 320 grit paper. A couple of additional applications were needed to make sure any imperfections were addressed, Do NOT prime it. (Details discussed in prior post)

2. Before covering, masking tape was applied parallel to the opening and about an inch to inch and a half away to establish a sharp demarcation line for the Poly Tak. A generous coat was applied on the surface that would contact the cover and left to dry. A second coat was then applied. Don’t forget to remove the masking tape before putting the fabric cover in place.

DSC_0201.jpg

3. After the fuselage is covered and pre shrunk (avoiding the glued area) to 250 degrees the Poly Tak can be activated with MEK. I used the MEK rather generously to assure good adhesion, and let it dry overnight before proceeding. You can see the color change when the Poly Tak soaks through signaling it is working. There were a few small spots where it did not appear to stick and those were of no concern.

DSC_0221.jpg

4. Pencil lines were drawn where cuts were to be made to facilitate wrapping the fabric. It must be wrapped into the recessed lip where the door fits, then around and under the back side of the opening. The pencil lines were coated with a thin line of Poly Tak and permitted to dry before cutting with a straight scissors, rather than pinking shears. The Poly Tak prevented fraying.

DSC_0222.jpg

5. The fabric was first glued to the recess with aid of the hobby iron. After it had set up well, the fabric was glued to the opening. After that the ‘tail’ was cut about a half inch beyond the inside opening with a pinking shear and then glued to the underside of the opening in sections about 4 inches long to make it easier to work with. A section of aluminum was used as a tool to push the fabric in place on the back side of the opening as it dried. This took some time.

DSC_0223.jpg

6. When finished, the opening was wiped down with MEK to assure a smooth surface, being careful not to use too much or the glue will soften and it will come apart. The final shrink to
350 ^ was done before moving on to the application of the grommet.

DSC_0226.jpg

7. The grommet was set in place and centered, using the longeron on top and the stringer below as reference points. It was temporarily taped in place and a pencil line drawn around the outside.

DSC_0229.jpg

8. Two coats of Poly Brush were applied along the outer surface as well as the surfaces around the opening where the fabric would contact, allowing time to dry between coats. A third coat was applied to just the outer surface and the grommet applied.

9. Once dry, cuts were made, making the cuts in different location than the underlying fabric so there would be at least one layer of fabric covering all surfaces. Using the Poly Brush the fabric was glued down. To hold the fabric on the back side of the lip, a short piece of aluminum was used, moving it inward as the Poly Brush set up. This took some time.

DSC_0279.jpg

10. Finally any bubbles or imperfections were ironed out with the hobby iron set around 180 to 200^. A final coat of Poly Brush was applied. Job done.

DSC_0287.jpg